The invention relates to a process for compacting granular molding materials and an apparatus necessary for implementation of the process.
Swiss Patent Specification No. 657,792 discloses a process and an apparatus for compacting granular molding material. The apparatus comprises a second frame which is arranged around the molding box and together with a hood arranged above the second frame, forms a pressure chamber. In the intermediate space between the molding box and the frame of the pressure chamber there is arranged either the granular material, such as for example molding material, or a liquid or pasty mass in a flexible cover. Consequently, the compacting pressure generated in the pressure chamber also acts on the outer walls of the molding box, so that there is an equalization of the compressive forces acting on the molding box walls. This makes possible the use of lighter molding boxes having lower strength values. A disadvantage associated with the foregoing is that the pressure chamber produced by the additional frame around the molding box and filling frame has to be of a correspondingly large design, which is very expensive and increases the dimensions of the molding machine. In addition, part of the compaction energy generated must be used for the pressure on the molding box from the outside.
Accordingly, it is the object of the present invention to provide a process and an apparatus for carrying out the process which makes it possible to use lightweight molding boxes of low stability wherein the pressure chamber is fitted in a sealed manner directly on the filling frame mounted on the molding box.